<template>
    <scroll class="listview" 
    :data="data" 
    ref="listview" 
    :listen-scroll="listenScroll"
    :probe-type="probeType"
    @scroll="scroll"
    >
        <ul>
            <li v-for="group in data" class="list-group" ref="listGroup">
                <h2 class="list-group-title">{{group.title}}</h2>
                <ul>
                    <li @click="selectItem(item)" v-for="item in group.items" class="list-group-item">
                        <img class="avatar" v-lazy="item.avatar"/>
                        <span class="name">{{item.name}}</span>
                    </li>
                </ul>
            </li>
        </ul>
        <div class="list-shortcut" @touchstart="onShortcutTouchStart" @touchmove.stop.prevent="onShortcutTouchMove">
            <ul>
                <li v-for="(item,index) in shortcutList" class="item" :class="{'current':currentIndex===index}" :data-index="index">
                    {{item}}
                </li>
            </ul>
        </div>
        <div class="list-fixed" ref="fixed" v-show="fixedTitle">
            <div class="fixed-title">{{fixedTitle}}</div>
        </div>
    </scroll>
</template>

<script type="text/ecmascript-6">
import Scroll from "base/scroll/scroll";
import { getData } from "common/js/dom";

const ANCHOR_HEIGHT = 18;

export default {
  props: {
    data: {
      type: Array,
      default: []
    }
  },
  data() {
    return {
      touch: {},
      listenScroll: true,
      scrollY: -1,
      currentIndex: 0,
      listHeight: []
    };
  },
  created() {
    this.touch = {};
    this.listenScroll = true;
    this.listHeight = [];
    this.probeType = 3;
  },
  mounted: function() {
    console.log("listview传入的data", this.data);
  },
  methods: {
    selectItem(item){
        this.$emit('select',item)
    },
    //触屏点击事件
    onShortcutTouchStart(e) {
      let anchorIndex = getData(e.target, "index");
      console.log(e, anchorIndex);
      let firstTouch = e.touches[0];
      this.touch.y1 = firstTouch.pageY;
      this.touch.anchorIndex = anchorIndex;

      this.currentIndex = parseInt(anchorIndex);

      this.$refs.listview.scrollToElement(this.$refs.listGroup[anchorIndex], 0);
    },

    //触屏滑动事件
    onShortcutTouchMove(e) {
      console.log("ggg");
      let firstTouch = e.touches[0];
      this.touch.y2 = firstTouch.pageY;
      let delta = ((this.touch.y2 - this.touch.y1) / ANCHOR_HEIGHT) | 0;
      let anchorIndex = parseInt(this.touch.anchorIndex) + delta;

      this.$refs.listview.scrollToElement(this.$refs.listGroup[anchorIndex], 0);
    },
    refresh () {
      this.$refs.listview.refresh()
    },

    scroll(pos) {
      console.log(pos);
      this.scrollY = pos.y;
    },

    //计算每个姓名歌手块的高度
    _calculateHeight() {
      this.listHeight = [];
      const list = this.$refs.listGroup;
      let height = 0;
      console.log("this.$refs.listGroup", list);
      this.listHeight.push(height);
      for (let i = 0; i < list.length; i++) {
        let item = list[i];
        height += item.clientHeight;
        this.listHeight.push(height);
      }
      console.log("listHeight数组", this.listHeight);
    }
  },
  watch: {
    data() {
      setTimeout(() => {
        this._calculateHeight();
      }, 20);
    },
    scrollY(newY, oldY) {
      console.log("滑动前的值:" + oldY, "滑动后的值：" + newY);
      const listHeight = this.listHeight;

      //当滚动在顶部
      if (newY > 0) {
        this.currentIndex = 0;
        return;
      }

      //当滑动在中间
      for (let i = 0; i < listHeight.length - 1; i++) {
        let h1 = listHeight[i];
        let h2 = listHeight[i + 1];
        if (-newY > h1 && -newY < h2) {
          this.currentIndex = i;
          console.log(i);
          return;
        }
      }
    }
  },

  computed: {
    shortcutList() {
      return this.data.map(group => {
        return group.title.substr(0, 1);
      });
    },

    fixedTitle() {
        if (this.scrollY > 0) {
          return ''
        }
        return this.data[this.currentIndex]?this.data[this.currentIndex].title:''
    }
  },
  components: {
    Scroll
  }
};
</script>


<style scoped lang="stylus" rel="stylesheet/stylus">
@import '~common/stylus/variable';

.listview {
    position: relative;
    width: 100%;
    height: 100%;
    overflow: hidden;
    background: $color-background;

    .list-group {
        padding-bottom: 30px;

        .list-group-title {
            height: 30px;
            line-height: 30px;
            padding-left: 20px;
            font-size: $font-size-small;
            color: $color-text-l;
            background: $color-highlight-background;
            text-align: left;
        }

        .list-group-item {
            display: flex;
            align-items: center;
            padding: 20px 0 0 30px;

            .avatar {
                width: 50px;
                height: 50px;
                border-radius: 50%;
            }

            .name {
                margin-left: 20px;
                color: $color-text-l;
                font-size: $font-size-medium;
            }
        }
    }

    .list-shortcut {
        position: absolute;
        z-index: 30;
        right: 0;
        top: 50%;
        transform: translateY(-50%);
        width: 20px;
        padding: 20px 0;
        border-radius: 10px;
        text-align: center;
        background: $color-background-d;
        font-family: Helvetica;

        .item {
            padding: 3px;
            line-height: 1;
            color: $color-text-l;
            font-size: $font-size-small;

            &.current {
                color: $color-theme;
            }
        }
    }

    .list-fixed {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;

        .fixed-title {
            height: 30px;
            line-height: 30px;
            padding-left: 20px;
            text-align :left;
            font-size: $font-size-small;
            color: $color-text-l;
            background: $color-highlight-background;
        }
    }

    .loading-container {
        position: absolute;
        width: 100%;
        top: 50%;
        transform: translateY(-50%);
    }
}
</style>

